Filter apparatus control



Sept. 23, .1958 I w. B. PE TE 2,853,155

FILTER APPARATUS CONTROL Filed April 1, 1955 INVENTOR.

W/LL/AM 8.1 5751? ATTORNEY United States Patent Qfiiice 2,853,155Patented Sept. 23, 1958 FILTER APPARATUS CONTROL William B. Peter,Louisville, Ky., assignor to American Air Filter Company, Inc.,Louisville, Ky., a corporation of Delaware Application April 1, 1955,Serial No. 498,711 1 Claim. (Cl. 183-62) Number 447,847 filed on August4, 1954 and now U. S. Patent 2,807,330 for Method and Apparatus forFiltering Air, there is described and claimed a filter providing acompressed web rolled upon a spool, the web being unwound from the feedspool across an air stream and simultaneously expanded in condition toact as a filter; and the spent web is rewound in compressed conditionupon a receiving spool. In a filter apparatus of this type at a giveninstallation, the rate of feed of the web is correlated to the filterarea, the feed being intermittent. The actuation of the web feedmechanism may be controlled by a differential pressure switch whichactuates the feed mechanism when the pressure drop across the filter webreaches or exceeds a certain value, and which de-energizes the feedmechanism when the pressure drop falls below that value.

In some installations it is desirable to actuate the web feed means by atimer. The period of operation of the web feed mechanism is quite slow,on the order of about 6 /2 to 29 lineal inches per week of 70 hours,equivalent to about .09 in. per hour to .4 in. per hour. A timer forthis purpose therefore must be exceedingly accurate, and must beadjustable through a wide time range. Such timers are commerciallyavailable but are relatively expensive.

It is an object of the present invention to provide an inexpensiveautomatic renewable type filter operated at timed intervals.

A further object is the provision of an inexpensive control mechanismfor an automatic renewable filter in which the filter medium is advancedperiodically in small increments.

Another object is the provision of a feed control mechanism tor a filterwhich is inexpensive and reliable in action.

The present invention employs a pair of continuous repeating cycletimers connected in series, so that the first timer operates the secondtimer at intervals, and the second timer accumulates operating time andactuates the feed mechanism intermittently. Repeating cycle timers ofthis type are commercially available and are relatively inexpensive.They operate in a continuously repeating cycle of opening and closing anelectrical switch or contact. In such a timer the percentage of the timeof a cycle during which the switch is closed is adjustable. However, inthe arrangement of the present invention, it is preferred that thesecond timer which actuates the feed mechanism, is maintained at a fixedadjustment, and adjustment of the first timer is employed to vary theoperating time of the second timer and of the feed mechanism. Thisstructure has the advantage that the timer and feed time are easilyadjustable and the apparatus employed is inexpensive.

The invention will be described in greater detail in the followingspecification taken in connection with the accompanying drawingsillustrating a preferred embodiment by way of example,.'and wherein:

Figure 1 is a partly diagrammatic side elevation of a filter embodyingthe invention; and

Figure 2 is a wiring diagram to explain the operation of the invention.

Referring to the drawing, Figure 1, the type of filter,'

shown by way of example, comprises a frame 1 having an openingtherethrough over which moves a filter web 3.

The web 3 may be of any suitable type, such as, for ex-' ample,.mattedor interwoven glass fiber, and at the top, is

unwound from a supply roll 4, on which it has been wound in compressedcondition. The web 3 is supported by a suitable perforate web orconveyor as it moves vertically across the opening, thearrangementallowing the web to fluff up on the conveyor, and at thebottom the web is rewound in tightly compressed condition on a rewindspool 5, which is driven, through suitable power transmission mechanism,by a motor 6. This structure is the subject matter of said Riverspatent, and as it forms no par-t of the present invention, it need notbe described here in further detail.

In such filters, the operative area of the filter medium is a functionof the height and width of the filter opening, and assuming a constantwidth, the area will vary as the height. The rate of feed of the web ofsuch a filter is quite small, and may vary from about 6 /2 inches perweek of seventy hours, to about 29 inches per week, for an equal width,depending on the height of the filter opening employed. The motor 6,which operates the rewind spool and thus determines the rate of feed, isoperated at only short intervals.

Referring to Figure 2, the filter medium 3 is diagrammatically shown asdriven by motor 6, and a fan or blower 7, driven by motor 8, maintains astream of air to be filtered passing through the filter. This motorreceives its power from electrical leads 9 and 10. Connected switches11, 12 are provided, the switch 11 being closed so as to excite a lamp13 which serves to indicate when the filter apparatus is not operating.A pressure sensitive vane 14 is so arranged that it is responsive to thestream of air, and when the blower is operating the vane 14 acts toshift switch 12 to closed position and open switch 11 to deenergizelight 13. The first cycle control timer 15 has a synchronous motor 16which drives a cam 17 that closes switch 18 for a predetermined periodof a cycle, that can be varied. Thus, for example, the timer 15 may beset to hold switch 18 closed for seven seconds out of each twelveminutes.

When switch 18 is closed, the motor 19 of the second timer 20 isenergized, and this motor in a similar way will keep switch 21 closedfor a predetermined period out ofeach twelve minutes of operation. Motor6 is operated when relay coil 22 is energized to close switch 23. Thisrelay coil can be energized by a manually operated switch 24 which isprovided for use in changing rolls. However, in operation, relay coil 22is energized by closing of. timer switch 21. As each timer motor 16 and19 has a cycle time of twelve minutes, and assuming timers 15 and 20 areeach to close switches 18 and 21 for seven seconds on each cycle, itwill require 713 seconds of operation of timer motor 16 before timermotor 19 is in position to close switch 21 for the first time. That is,when switch 18 completes closing and opening for the l02nd time it willhave operated timer motor 19 fora total of 714 seconds. As 713 secondsof operation of motor 19 are necessary before switch 21 is closed, itwill be seen switch 21 will be closed for one second, and thereforemotor 6 is operated for one second. The next time switch 18 closes,which will be in 713 seconds, motor 19 will again be operated for 7seconds, and during six of these seconds switch 21 will be closed tooperate motor 6. Thus, at the end of about twenty and three fifths hoursintervals, motor 6 is operated for seven seconds, and on the average,for each seventy hours of operation of the air filter, the filter web isadvanced 6 /2 inches. The rate of advance of the filter web can beadjusted by varying timer 15 to provide a longer or shorter closing timefor its switch 18. Thus, for example, by varying the setter of timer 15from 7 to 29 seconds, the feed can be varied from 6 /2 inches per 70hour week to 29 inches per week. That is, each second setting of timer15 corresponds to one inch per week web feed. This ratio, of course, canbe varied as desired.

When the blower 7 is stopped, the vane 14 opens switch 12 to stop thetimer operation. The timers therefore accumulate time only while thefilter is in operation.

I claim as my invention:

A filter medium feed control comprising normally inoperative motorizedfilter medium feeding means, first repeating cycle timing meansoperative in responseto air flow through said filter medium, firstswitching means controlled by said first repeating cycle timing meansand arranged to be selectively actuated thereby during a predeterminedportion of each of said repeating time cycles thereof, second repeatingcycle timing means operative in response to and in accordance with theperiods of actuation of said first switching means, second switchingmeans controlled by said second repeating cycle timing means andarranged to be selectively actuated thereby during a predeterminedportion of each of said repeating time cycles thereof and meansresponsive to the periods of actuation of said second switching meansfor rendering said motorized filter medium feeding means operative toadvance filter medium during said periods of actuation.

' References Cited in the file of this patent UNITED STATES PATENTS1,638,067 Szekely Aug. 9, 1927 2,152,900 Manning Apr. 4, 1939 2,626,012Persons Jan. 20, 1953 2,687,173 Loft Aug. 24, 1954 2,722,998 Hall Nov.8, 1955 i

